Automatic telephone system



Feb. l5, 1938. A. HEYDUCK AUTOMATI TELEPHONE SYSTEM Filed Nov. 23, 1935 Patented Feb. 15, 1938 AUTOMATIC TELEPHONE. srsrslu Alfred Heyduck, Berlin-Neuenhagen, Germany, assigner to Mix & Genest Aktiengesellschaft, Berlin-Schoneberg, Germany, a company Application November 23, 1935, Serial No. 51,252 In Germany November 28, i934 `6 Claims.

from theoutsde exchange line, while connecting it tothe selectors of a local trunk, the outside' connectionrbeing maintained at that time in a well-known manner. The user of Asuch a P. B. X. station can in this way make an intermediate call to a. subscriber whose station isconnected to the A P. B. X., but he can not make an intermediate call toanother outside exchange subscriber, that is to say, can not make an intermediate .call over the main exchange.

"Facilities for intermediate call over the main exchange are provided in the arrangement described hereafter by way of example, reference beingY had to theY accompanying drawing, that diagrammati'cally shows a private branch exchange system consisting of local trunks or links AS-LW and outside exchange trunk equipments AW. Only one local trunk and one outside trunk are shown. N denotes a subscribers set. Relays are designated by capital letters, their contacts by the respective small letters.

A.-Loccl calls within P. B. X.

Uponlifting the receiver, relay R,be1onging to station N, pulls up:

wiz, r11, N, tlv, RI,

lIn this same test wire circuit the windings II `of relays R and T of the subscriber are energized. Contacts tII and tIII as well as con-k tact lrII switch off the windings and resistances Wil, RI, .TI which were connected with the-talking path during the calling condition. NH is also `deenergized over Contact IIV. Relay PA pulls up and with its contact pal short-circuits the high resistance .portion of its winding, whereby the calling subscriber is blocked in known manner against the hunting of all selectors. Contact paII breaks the circuit of the call iinder, so that fkthe switching arms of AS will stop at the segments `oi the calling subscriber. Contacts PaIII and pctIV switch the talking wire through, so that relays AH and BH can pull up over the subscribers loop, i. e. over station N. Contact altIII closes a circuit for VAI-I over yhI, ahIII, VAH, Instead of contacts paIII and paIV, contacts cwh and tahII close the circuit to the subscriber. pole directly to the c-wire, so that relay PA releases; In the local trunk contact ochV had switched the starting chain onto the next free local trunk. With this operation relay EH has released and has therefore opened its contacts chl and vehII.

Relays AH and 'BI-I swing with the dialing. In this operation only those circuits become effective which are joined with the contacts of relay AH. Relay VBH pulls up during the series of impulses;

because contact ahIII removes the short circuit l of this relay, y Relay VBH is retarded against release and consequently remains pulled up during the impulse series, as does relay VAH. Contact altI energizes line selector magnet LWM over Dahl/'II according to the number of impulses given, so that the line selector turns its switching arms a, b, c the desired number of steps. At the end of the series of impulses, relays AH and BI-I remain again permanently pulled up. Relay VBH releases at the end of its retardation period because the short circuit of its winding is now again permanently established. With the release lof VBH, suitably built contacts 'UbhIV and obhHI thereof are operated consecutively, so that potential is temporarily switched on the windings of PL. This establishes the test circuit, in which relays R and T of the desired subscriber are energized over their windings II. Relay PL pulls up and short-circuits the high resistance portion of its winding, so that it blocks in known manner the called subscriber against engagement over other selectors. It holds over its low resistance winding II .and contacts plIlI, oahIV. Contacts plI and plII switch the talking wires of the house connection set through to switching arms c and h of line selector LW; Call current is now transmitted periodically into the line to the called party from a source of alternating current, so that the ringer will operate there. The call current .flows through the windings of relay YH, which Contact odhIII switchesthe positive n however can not pull up because its Winding II is short-circuited through vbhII. As soon as the called subscriber lifts the receiver, a direct current circuit is closed over the subscribers loop and the windings of relay YH, under the effect oi' which relay YH pulls up. Contact yhI removes the short circuit of relay VBI-I, so that the latter pulls up. Contact cbhV switches relay YH from the source of alternating current and connects it directly to the positive pole. Contacts vbhI and 'ubhII switch the talking path between the calling and the called parties through, so that now the telephone connection is established.

At the end of the call both subscribers replace their receivers, and relays AH, BH, YH release. Relay VAH is thereby deenergized and therefore over UahIII and vahIV it removes the busy potential from the c-wires of the call finder and the line selector. As soon as PL is released, a circuit is established for LWM over:

UahVII, pZIV, lwm, lcoh Contact lach is open as long as the line selector is in the rest position, and it closes as soon as this selector leaves that position. Contact lwm is controlled by the armature of the line selector, so that it operates as a selfinterrupter. The line selector turns until it reaches its rest position, whereupon contact koi/z opens and stops the selector. The local trunk thereby becomes free again for further seizures.

B.-Calls from P. B. X. to Outside exchange The drawing merely shows the devices for outside exchange traiie. Incoming traiiic from the outside exchange has not been considered, since it is immaterial to the nature of the invention.

If a subscriber wishes to establish an outside exchange connection, he lifts the receiver and operates the key n at his station, thereby grounding the talking wires. Therefore relay R can not operate due to short circuiting, while on the other hand relay T pulls up over its winding I due to amplification of current and holds, after the release of the key, over Tl, 7H, N, tIII, TIII, NA, -I-

so that outside trunk starting relay NA responds. If a call iinder AS has already tested when the subscriber presses his grounding key, then, through the grounding of the connection line, relay BH of this call finder is caused to release through short circuiting and relay XH of the respective local trunk is energized over its winding II:

+, ahII, hhI, XI-III,

The c-wire is interrupted at the rest contact of rhII, so that subscriber relays R and T, which in this special case have been energized over the c-wire of AS and their windings Il', are caused to release, and the a-wire is grounded over vahIII at the front contact of hII. Consequently relay R can not pull up again over its winding I due to short circuiting, while TI is sufficiently energized over the direct ground to pull up and it will hold over tIII in series with exchange starting relay NA. At h relay VAH is caused to release slowly through short circuiting. Contacts oahI, oehII open and relays AH, BH and XHI release, so that the local trunk becomes free. The subscriber relays are now in the same condition as if the grounding key had been pressed before the testing of the call nder, and relay NA is therefore operated in this case also.

Relay NA closes, with its contact nal, a circuit for relay E in the first free outside trunk equipment. Contact eI prepares the test path over the d-arm of the outside trunk selector, and contact eII closes the circuit for rotary magnet AWM of the outside trunk selector, which turns step by step as a self-interrupter until its switching arms meet the connection of the calling subscriber. The test circuit is thereby established over RII/TII, rI, tI, d-arm of AW, pIII, PI, PII, cI,

Relay R pulls up and thereby separates the calling equipment from the loop of the calling subscriber. Relay P short-circuits the high resistance portion of its winding, so that the subscriber is blocked in known manner against seizure over other selectors. At contact pV it opens the circuit for AWM. Contact pIII switches relay P from the d-wire and connects it with the c-wire, so that RII and TII now are held without the aid of contacts tI, TI. Contacts pI, pII switch the telephone path frorn the subscriber to supply bridge A, B. The two relays pull up; A switches in relay VA, with its contact aIII, over VA, am, xn,

Contacts cal, 'UaII now assume the switching and in this way releases P through short circuiting. Contact vaIV, in preparation, is switched to connect the outside trunk start chain to the relay of the next exchange connection set; consequently relay E releases and, by its contact eI, definitely breaks the circuit for P.

With contact al relay A has closed, over the winding of the repeating coil RU, the loop line leading to the outside exchange, so that the call condition is produced at the outside exchange in known manner.

If the outside exchange is of the automatic type, then the subscriber will dial, in which case contact aI transmits the impulses to the outside exchange. While dialing, VB pulls up over This relay holds because it is retarded against release during each series of impulses, and over ubI it short-circuits repeating coil RU, in order to prevent any distortion of impulses. At the end of the outside exchange call the subscriber replaces the receiver; A and B release and cause the release of VA, which hence removes the busy potential from the c-wire of the subscribers line. Contact aI breaks the loop leading to the outside exchange, so that the clearing signal will be given there in known manner.

C.-An intermediate call during outside call In order to establish an intermediate call connection the subscriber presses the key n at his station N and thereby grounds the talking wire. Relay B therefore releases, so that X pulls up over aII, bI. Contact x1 in preparation short-circuits the outside exchange loop over rI, ubI, in order to preclude any interruptions. Contact acII removes the short circuit of VB, which therefore pulls up, so that now switching relay UA is energized as follows: scII, vbII/vaVIII, UAI/W. On releasing the key, B releases again and hence switches off X. VB releases again. UA continues to hold over:

The direct current loop to the exchange continues to be maintained over ual after the release oi X. At the same time the short circuit around UB is interrupted byudl so that this relay can pull upr under the influence ci the exchange current. Contacts uaI and uaIII switch the outside trunk line from the' repeating coil and connect the intermediate call line Q in its place. Relay RR oi th-e intermediate call line pulls up:

Local trunk starting relay NH is energized over rrIV and ttIV. Exactly in the same manner as described in connection with local calls within P B. X., the call iinder of a free local trunk now moves and finds the intermediate call line. The subscriber selects in known manner the subscriber desired for the call back. At the end of the intermediate call the subscriber switches back to the exchange line by again pressing the key at his station. Relay B thereby again releases so that relay X is cut in by contact b1. Contrary to the rst pressing of the key, relay VB can not pull up. now, since it continues to be short-circuited over obIII, ubII, aIII. Holding winding II of relay UA is short circuited at :cIIL so that UA releases. This breaks the direct current loop to the local trunk used in the intermediate call and the seized local trunk is released.v The outside trunk line is 4again switched through to the subscriber by the release of X.

D.-An intermediate call over a second outsid trunk: line If the calling subscriber, talking with an outside exchange subscriber, wishes toV make an intermediate call to another outside exchange subscriber instead of to a subscriber connected to the P. B. X. system, then he will by means ci key 1i rst switch, in the before described manner, from the outside trunk line to the intermediate call line Q so that a free local trunk will be seized. He will now dial a. certain special number, thereby setting line selector LW to a contact to which is connected merely the windingY I of relay 'XI-lof the local trunk itself. XH pulls up over the c-wire and test relay PL. The pulling up of relay XII `has now the same veiect as described before under Calls from P. B. X. to outside exchange with respect to the case wherein the call finder had already taken the position of the calling'connection before the subscriber had pressed the grounding key ior the purpose of starting an outgoing exchange connection. Contact 33h11 breaks the holding circuit leading to RRII and RTII, so that Vthese two relays release for the present, and at the same time it connects positive potential over vahIII to the a-wire of the local trunk. Therefore, BH releases and thus keeps relay XH energized over ahII, bhI, XI-III. Contact xliI shortcircuits relay VAH, which releases at the end of its retardation period and hencedisconnects the talking wire by means of contacts Dahl', vchII. Consequently AH causes the release o relay XH. The local trunk is released. When Contact :chil connected positive potential to the a-wire of the local trunk, relay RR could not pull up again, due to short circuiting, while RT was energized over its winding I due to current amplication and locked over TtIII and outside-trunk starting relay NA. Relays RT and NA continue to hold `even after vahIII hasV removed the positive potential from the a-wire. The switching condition is consequently the same as if a subscriber wanted to reach a free outside-trunk for an outgoing connection, only that now an intermediate call connection is to be considered instead of a subscribers connection. As described with reference to outgoing exchange trac, a free outside trunk selector AW starts to move now and finds the intermediate call line. The subscriber can now dial the desired outside exchange subscriber over this second outside trunk line and is in a position to make the intended intermediate call. As can be seen from the foregoing, this intermediate call connection runs over the switching arms ofthe original AW, the intermediate call line of this AW and the switching arms of the second outside trunk selector AW directly without a local trunk being comprised in the connection. At the end of the intermediate call, as already described, the key at the station is again pressed, whereby the subscribers line is switched off from the intermediate call connection and is again connected with the rst outside Ytrunk line which was waiting in the meantime. The second outside trunk line used Y for the intermediate call is consequently released.

What is claimed is:

i. In a branch exchange system having local lines', outside trunks, common local trunks accessible to any of said local lines for establishing V@the connections from one local line to another,

outside-trunk switching apparatus for establishing connections from a local line to an outside trunk and rst discriminating means normally effective to associate said outside-trunk apparatus with a calling local line in response to the grounding of the calling local line, theV combination which comprises an intermediate-call line, second discriminating means responsive to a Agrounding of the calling line after the establishment of a first connection to a first outside trunk for temporarily disabling said connection and initiating an intermediate-call connection over said intermediate-call line and over one of said local trunks; other means responsive to a later grounding `ci the calling line during the intermediatecall connection for releasing said intermediatecall connection and resuming said rst connection and third discriminating means associated with said local trunk and responsive to the setting up of a particular number in said local trunk for releasing said local trunk and grounding said intermediate-call line whereby an intermediatecall from said calling branch exchange station over a second outside trunk is established by the actuation of said iirst discriminating means without actuating said second discriminating means so as to resume the previously established connection to said iirst outside trunk.

2. A telephone system comprising an outside exchange, a branch exchange, outside trunks extending from said branch exchange to said outside exchange, branch stations, lines connecting said branch stations to said branch exchange, an impulsing device and a grounding device at each .of said branch exchange stations, local trunks for interconnecting said lines responsive to signals from, the impulsing device. at the calling branch station, discriminating means normally responsive to the actuation of the grounding device at a calling branch station for initiating the establishment of a connection over one of said outside trunks, intermediate-call means including an intermediate-call line and a ground-detecting apparatus, said apparatus being responsive to the actuation of the grounding device at the calling branch exchange station after the establishment of a rst outside connection from said station to a first outside trunk for temporarily disabling said first outside connection and initiating an intermediate-call over said intermediate call-line, said discriminating means being also responsive to the reception of a predetermined set of impulses from the impulsing device of the calling branch station during the connection of said calling station over said intermediate-call line to one of said local trunks to ground the intermediate-call line, release said local trunk and initiate the establishment of a connection over a second of said outside trunks.

3. A telephone system comprising an outside exchange, arr automatic branch exchange, branch exchange stations, branch exchange lines connecting said stations to said branch exchange, switching arrangements in the branch exchange whereby any one of said lines may be connected to any other of said lines, outside trunks extending from said branch exchange to said automatic outside exchange, an intermediate-call line, further switching arrangements within the branch exchange whereby any one of said lines including said branch exchange lines and said intermediate-call line may be connected over any one of said trunks to the automatic outside exchange, and means whereby an automatic branch exchange line which is engaged in a first connection with a rst outside trunk may be intermediately connected over said intermediate-call line and said further switching arrangements to an idle second outside trunk for establishing an outward call to said outside exchange over said second trunk while maintaining established the connection between said exchange line and said i'lrst outside trunk.

4. A telephone system according to claim 3 further comprising a grounding device at each of sa-id branch exchange stations and means at the branch exchange responsive to the operation of the grounding device of the calling exchange station at the termination of an intermediate call for releasing the intermediate call connection and rendering operative the connection between said station and said rst outside trunk.

5. A telephone system according to claim 3 having a grounding device at the calling branch exchange station and means responsive to the operation of said device after the initiation of an intermediate-call for releasing said intermediatecall and resuming the previously established rst connection with ther iirst outside trunk, which further comprises special transfer apparatus responsive to the grounding of any calling line and switching means associated with a predetermined path of the branch exchange and adapted to ground said intermediate-call line responsive to the selection of said predetermined path, whereby the said transfer apparatus is actuated.

6` A telephone system according to claim 3 in which each branch exchange line is associated with a line relay and a cut-oi relay and in which the said intermediate call line is associated in like manner with a similar line relay and a similar cut-olf relay, these last named relays being connected in the same manner as said first named relays.

ALFRED HEYDUCK.

Cil 

